Our research approach is to understand the virulence of Trichomonas vaginalis through the identification and biochemical characterization of membrane immunogens with important biological properties or functions. Four major areas of research are emphasized: i) immunochemical membrane analysis of numerous long-term grown and fresh isolates targeting key antigens as molecules governing heterogeneity; ii) assessment and identification of (membrane) antigens shed or secreted by pathogenic trichomonads; iii) parasite cytadsorption to host cells; and finally iv) continued examination of the interaction between specific host macromolecules and T. vaginalis. Numerous methodologies will be employed which include standard radiolabeling procedures, chromatographic and electrophoretic methods, centrifugation-gradient procedures, antibody reagents, sensitive and specific radio-immunoprecipitation assays, and fluorescence-Nemarski-electron microscopy. Our overall objective is to identify highly immunogenic membrane antigens of T. vaginalis which possess key biologic functions, such as ligands involved in host cytadherence or receptors of specific host proteins, both processes essential for infection of human hosts. Studies in our laboratory presented in the Preliminary Results section continue to show the progress and feasibility of our plan at understanding this host-parasite relationship and using the pathogenic human trichomonads as models.